From d526323ce24a5dfb63c369aa0caa4ebb6f951792 Mon Sep 17 00:00:00 2001
From: Simon Duquennoy <simon.duquennoy@ri.se>
Date: Sat, 24 Feb 2018 15:35:58 -0800
Subject: [PATCH] CSMA for Cooja motes: increase backoff_period

---
 os/net/mac/csma/csma-output.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/os/net/mac/csma/csma-output.c b/os/net/mac/csma/csma-output.c
index 65403324e..74803ecf1 100644
--- a/os/net/mac/csma/csma-output.c
+++ b/os/net/mac/csma/csma-output.c
@@ -154,9 +154,15 @@ neighbor_queue_from_addr(const linkaddr_t *addr)
 static clock_time_t
 backoff_period(void)
 {
+#if CONTIKI_TARGET_COOJA
+  /* Increase normal value by 20 to compensate for the coarse-grained
+  radio medium with Cooja motes */
+  return MAX(20 * CLOCK_SECOND / 3125, 1);
+#else /* CONTIKI_TARGET_COOJA */
   /* Use the default in IEEE 802.15.4: aUnitBackoffPeriod which is
    * 20 symbols i.e. 320 usec. That is, 1/3125 second. */
   return MAX(CLOCK_SECOND / 3125, 1);
+#endif /* CONTIKI_TARGET_COOJA */
 }
 /*---------------------------------------------------------------------------*/
 static int